149 - Treatment of extra canal lumbosacral nerve root entrapment by unilateral biportal endoscopy through extraforaminal approach

Objective To investigate the effect of unilateral biportal endoscopy (UBE) through extraforaminal approach in the treatment of extra canal lumbosacral nerve entrapment. Methods Seventeen patients with extra canal lumbosacral nerve root entrapment were treated by UBE through extraforaminal approach in Tianjin Hospital from January 2020 to March 2022, including 9 males and 8 females with an average age of 59.2 years (range 45-71 years). All 17 patients had lower limb radiation pain, numbness, and weakness with or without intermittent claudication. MRI imaging examination showed L4/5 foramen stenosis with far lateral disc herniation in 2 case, and L5/S1 foramen stenosis with far lateral disc herniation in 15 cases, and the height of intervertebral space decreased, resulting in the compression of exiting nerve root and ganglion. Among them, far out syndrome was diagnosed in 7 cases and transitional lumbarsacral vertebrae was found in 12 cases. The incisions were designed 2 cm away form the projection of adjacent pedicles, while incision at S1 was designed at the inner edge of the iliac bone due to the shielding of the ilium, taking the outer edge of the isthmus at the outer opening of the intervertebral foramen as the target of channels. The ventral and apical part of superior articular process (SAP) was gradually removed with high-speed burr from its outer edge and isthmus, and the occluded sacral ala and the lower edge of transverse process were removed when necessary. The hyperplastic ligament was removed to expose the exiting nerve root. The protruding intervertebral disc was removed at the ventral side of the nerve root. The far out syndrome was decompressed laterally along the exiting nerve root until it is completely released. The results and stability were evaluated with visual analogue scale (VAS), Oswestry disability index (ODI), Macnab scores and dynamic X-ray film during follow-up.

Results: The operation time was 45-85 min, with an average of 60 min. After remove of the SAP tip and enlarge of the intervertebral foramen, the exiting nerve root and disc protrusion were fully exposed, the exiting nerve root was exposed and released laterally until totally release without entrapment in far out syndrome, and the nerve could be decompressed completely. The symptoms were significantly relieved after operation, and imaging examination showed that facet joints were preserved. During follow-up, the pain and function improved continuously. At final follow-up, the improve rate of VAS and ODI were 85.2% and 86.2%， respectively, and the results were excellent in 15 cases and good in 2 case according to Macnab score, and there was no lumbar instability on dynamic lumbar X-ray film. Conclusion Extra canal lumbosacral nerve entrapment can be treated by UBE through extraforaminal approach, with sufficient exposure, complete decompression and better preservation of lumbar stability.